Resin composition, metal foil with resin, metal-clad laminate, and capacitor element

Abstract

The resin composition contains covering particles and a resin. The covering particles have a core portion containing a metal oxide and a covering layer containing a hydrated oxide of aluminum disposed on the surface of the core portion. The metal oxide is represented by M x O y (where M represents at least one element selected from the group consisting of Ba, Ti, Sr, Pb, Zr, La, Ta, Ca, and Bi, and x and y represent numbers determined by stoichiometry according to the valence of the metal element M). When XPS analysis is performed on the particles contained in the resin composition, the atomic ratio Al / (M + Al) is 0.05 or more and 0.7 or less.

Description

Technical Field

[0001] The present invention relates to a resin composition. Further, the present invention relates to a metal foil with a resin, a metal-clad laminate, and a capacitor element having the resin composition. Background Art

[0002] With the miniaturization of capacitor elements, high electrostatic capacitance of the dielectric used in the capacitor elements is desired. In particular, high electrostatic capacitance of capacitor elements built in a printed circuit board is desired. A capacitor element built in a printed circuit board generally includes a resin layer containing dielectric particles and a binder.

[0003] In order to achieve high electrostatic capacitance of a capacitor element having such a structure, for example, thinning of the resin layer can be considered. However, if the resin layer is thinned, there may be a problem of a decrease in the dielectric breakdown voltage.

[0004] It is considered that high electrostatic capacitance of the capacitor element can also be achieved by increasing the relative dielectric constant of the resin layer. In order to increase the relative dielectric constant of the resin layer, it is easy to increase the filling rate of the dielectric particles contained in the resin layer. However, if the filling rate of the dielectric particles is increased, there may be an insulation failure caused by leakage current.

[0005] In addition to the above methods, in Patent Documents 1 and 2, a technique of covering the surface of dielectric particles with a compound of aluminum is also proposed.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2002-367856

[0009] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2020-57667 Summary of the Invention

[0010] In the technique described in Patent Document 1, the surface of the dielectric particles is covered with aluminum oxide. However, when the surface of the dielectric particles is covered with aluminum oxide, it is likely to cause a reaction with impurities (such as moisture), and it is difficult to stably control the covering state suitable for high electrostatic capacitance.

[0011] In the technique described in Patent Document 2, the surface of the dielectric particles is covered with a hydrated oxide of aluminum. However, in this document, aggregated granular hydrated oxide is generated, which may lead to an increase in the leakage current of the resin composition, and a decrease in the dispersibility of the particles in the resin and the adhesiveness of the resin.

[0012] Therefore, the object of the present invention is to improve a resin composition suitable for use as a dielectric layer of a capacitor element. More specifically, a resin composition with suppressed leakage current and sufficient adhesiveness is provided.

[0013] The present invention solves the above technical problems by providing a resin composition containing coated particles and a resin. The coated particles have a core portion containing a metal oxide and a coating layer containing a hydrated oxide of aluminum disposed on the surface of the core portion.

[0014] The aforementioned metal oxide is represented by M x O y (where M represents at least one element selected from the group consisting of Ba, Ti, Sr, Pb, Zr, La, Ta, Ca, and Bi, and x and y represent numbers determined by stoichiometry according to the valence of the metal element M).

[0015] When XPS analysis is performed on the particles contained in the aforementioned resin composition, the atomic ratio Al / (M + Al) is 0.05 or more and 0.7 or less.

[0016] In addition, the present invention provides a metal foil with resin, which includes a metal foil and a layer formed of the aforementioned resin composition provided on at least one surface of the metal foil.

[0017] Furthermore, the present invention provides a metal-clad laminate, which includes a first metal foil, a second metal foil, and a resin composition layer sandwiched between these two metal foils.

[0018] The resin composition layer is formed of a cured product of the aforementioned resin composition.

[0019] Furthermore, the present invention provides a capacitor element having the aforementioned metal-clad laminate. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 (a) of is a transmission electron microscope image of the coated particles obtained in Production Example 1.

[0021] Figure 1 (b) of has a transmission electron microscope image of the coated particles obtained in Production Example 1 after cross-section processing on the left side, and an elemental mapping image of the same field of view on the right side.

[0022] Figure 2 (a) of is a transmission electron microscope image of the coated particles obtained in Production Example 10.

[0023] Figure 2 (b) of has a transmission electron microscope image of the coated particles obtained in Production Example 10 after cross-section processing on the left side, and an elemental mapping image of the same field of view on the right side.

[0024] Figure 3 Analysis results based on XAFS (X-ray absorption fine structure analysis) of the coated particles obtained in Production Example 6 and Production Example 1. Detailed Description

[0025] Hereinafter, the present invention will be described based on preferred embodiments. The present invention relates to a resin composition. The resin composition contains specific particles and a resin, and is formed by dispersing the particles in a matrix containing the resin. Hereinafter, the particles and the resin will be described.

[0026] The particles contained in the resin composition of the present invention are composite particles having a core portion and a coating layer disposed on the surface of the core portion. Hereinafter, the composite particles will also be referred to as "coated particles".

[0027] The core portion in the coated particles is a portion that occupies most of the volume in the coated particles and is located in the central region of the coated particles. The core portion is composed of a metal oxide. As the metal oxide, a substance having a high relative dielectric constant is preferably used. In particular, from the aspect of the high relative dielectric constant of the metal oxide, the metal oxide is preferably composed of M x O y (M represents at least one element selected from the group consisting of Ba, Ti, Sr, Pb, Zr, La, Ta, Ca, and Bi. x and y represent numbers determined by stoichiometry according to the valence of the metal element M.)

[0028] In the metal oxide represented by M x O y the metal element represented by M may be used alone or in combination of two or more. In the metal oxide represented by M x O y when only one metal element represented by M is used, examples of the metal oxide include BiO, SrO, Pb(II)O, Pb(II) 2 Pb(IV)O 4 , Pb(IV)O 2 , ZrO 2 , La 2 O 3 , Ta 2 O 5 , TaO 2 , CaO, Bi 2 O 3 , TiO 2 and the like.

[0029] On the other hand, in the metal oxide represented by M x O yIn the case of using two or more metal elements represented by M in the metal oxide, examples of the metal element include a combination of a divalent metal element and a tetravalent metal element. Specifically, examples include combinations of Ti and Ba, Ti and Sr, Ti and Ca, Ti and Mg, Ti and Bi, Zr and Ba, Zr and Sr, Zr and Ca, Zr and Pb, etc. By adopting these element combinations, a metal oxide with a high relative dielectric constant can be obtained.

[0030] From the viewpoint of further increasing the relative dielectric constant of the metal oxide, the M element is particularly preferably at least Ti and at least one of Ba and Sr.

[0031] From the aspect of increasing the relative dielectric constant of the metal oxide, the metal oxide represented by M x O y is preferably a compound having a perovskite-type crystal structure. In particular, from the aspect of further increasing the relative dielectric constant of the metal oxide, the metal oxide represented by M x O y is preferably a compound having a cubic or tetragonal perovskite-type crystal structure. From this viewpoint, the metal oxide is preferably represented by the composition formula: (M1)(M2)O 3 (wherein the M1 element and the M2 element represent elements selected from the M element).

[0032] As the metal oxide represented by M x O y in the present invention, particularly preferred substances are BaTiO 3 , BaTi 4 O 9 , SrTiO 3 , Pb(Zr,Ti)O 3 , PbLaTiO 3 , PbLaZrO, SrBi 2 Ta 2 O 9 etc. It should be noted that Pb(Zr,Ti)O 3 refers to Pb(Zr z Ti 1-z )O 3 (where 0 ≤ z ≤ 1, typically 0 < z < 1).

[0033] The metal oxide represented by M x O yIn the represented metal oxide, for the purpose of further increasing the relative dielectric constant of the metal oxide, a metal element other than the M element may be contained in a trace amount. Examples of such a metal element include rare earth metal elements such as Y, Nd, Sm, and Dy.

[0034] Containing M x O y The surface of the aforementioned core portion of the metal oxide represented is covered with a covering layer. The covering layer is a layer containing a hydrated oxide of aluminum. The hydrated oxide of aluminum also includes so-called aluminum hydroxide, which is generally represented by the compositional formula: Al 2 O 3 ·nH 2 O (n represents a positive number) and / or the compositional formula: Al(OH) 3 The covering layer directly covers the surface of the core portion, or indirectly covers the surface of the core portion through a layer other than the covering layer.

[0035] The present inventors comprehensively investigated using analytical methods such as H-NMR, Al-NMR, AES, and XPS, and considered that in the hydrated oxide of aluminum, the particularly preferred structure in the present invention is Al 2 O 3 ·3H 2 O. Furthermore, by comparing the spectrum obtained using XAFS (X-ray absorption fine structure analysis) with the relevant references of aluminum compounds (for example, J.Synchrotron Rad. (1999) 6.621 - 623), the coordination structure of Al can be speculated. Based on these results, the present inventors consider that it is preferable for Al to have a six-coordinate structure. Examples of the structure in which Al has a six-coordinate structure include Bayerite, Gibbsite, Doyleite, Nordstrandite, etc.

[0036] In the present specification, the "covering layer" refers to a film-like portion existing on the surface of the core portion. Therefore, even if a hydrated oxide of aluminum exists on the surface of the core portion, when the existing state of the hydrated oxide is in an aggregated particulate form, the hydrated oxide does not belong to the "covering layer".

[0037] Whether a film-like portion containing a hydrated oxide of aluminum exists on the surface of the core portion can be determined by transmission electron microscopy observation and elemental mapping of the covered particles.

[0038] Regarding the covering layer, when performing elemental mapping of aluminum, as long as it exists in a film state on the surface of the core part to an extent that the outline of the core part can be recognized, the covering layer can continuously exist on the entire surface of the core part, or can also discontinuously exist in such a way that a part of the surface of the core part is exposed. The thickness of the covering layer is desirably uniform, but as long as it covers the surface of the core part in a film state, it can also be non-uniform.

[0039] The average thickness of the covering layer is preferably 1 nm or more and 40 nm or less, more preferably 1 nm or more and 20 nm or less, and still more preferably 1 nm or more and 5 nm or less. The average thickness of the covering layer can be measured as follows: Using a transmission electron microscope (TEM), the end part of the particle having the covering layer is erected (i.e., perpendicular to the observation surface) for elemental mapping, and the thickness is measured at randomly selected multiple places (for example, 10 places) from the Al part observed as a film, and the average value is calculated. It should be noted that during elemental mapping, FIB (Focused Ion Beam) or the like can also be used for cross-section processing as needed.

[0040] By covering the surface of the core part with a film-like part containing hydrated aluminum oxide, that is, the covering layer, when the resin composition of the present invention is used as, for example, a dielectric layer of a capacitor element, there are advantages that the leakage current is suppressed and thus the dielectric breakdown voltage becomes higher. In addition, there is an advantage that the dispersibility of the covering particles in the resin becomes good. In contrast, as can be seen from Comparative Example 1 described later, when hydrated aluminum oxide adheres to the surface of the core part in an aggregated particle state (see Figure 2 ), it is not easy to suppress the leakage current and improve the dispersibility of the particles in the resin.

[0041] From the viewpoint of further suppressing the leakage current or further improving the dispersibility in the resin, it is preferable that the covering layer directly covers the surface of the core part. Whether the covering layer contains hydrated aluminum oxide can be determined by measurements based on H-NMR, Al-NMR, AES, and XPS, and further by synchrotron radiation-based XRD measurement of radiation light.

[0042] From the viewpoint of further significantly suppressing leakage current, in the coated particles, it is preferable to control the coverage amount of the layer containing hydrated oxide of aluminum on the core. By controlling the amount of the coating layer, the dispersibility of the coated particles with respect to the resin is improved, whereby the leakage current is further suppressed. In addition, by improving the dispersibility of the coated particles with respect to the resin, when the resin composition of the present invention is used as the dielectric layer of a capacitor element, there is also an advantage that the adhesion between the resin composition and the electrode is good. The covering state of the coating layer on the core can be determined by various methods. The present inventors have found that among these methods, the composition of aluminum element and M element on the surface of the coated particles obtained by XPS (X-ray photoelectron spectroscopy), which is a method capable of observing the elemental composition on the outermost surface of a substance, most reflects the covering state of the coating layer on the core. Based on this insight, the present inventors further conducted research, and the results showed that when the resin composition of the present invention is subjected to XPS analysis, when the value of the atomic ratio Al / (M + Al) satisfies a specific numerical range, the dispersibility of the coated particles with respect to the resin is significantly improved. Specifically, when the resin composition of the present invention is subjected to XPS analysis, when the value of the atomic ratio Al / (M + Al) (hereinafter, this value is also referred to as "aluminum coverage ratio") is preferably 0.05 or more and 0.7 or less, the leakage current can be suppressed while significantly improving the dispersibility of the coated particles with respect to the resin.

[0043] The present inventors believe that the aluminum coverage ratio within the above range corresponds to the state where the coating layer thinly covers the surface of the core. If the coverage degree of the coating layer on the core is too large, there is a tendency that although the leakage current is suppressed, the dispersibility of the coated particles with respect to the resin decreases. On the other hand, if the coverage degree of the coating layer on the core is insufficient, it is difficult to suppress the leakage current. From these viewpoints, the aluminum coverage ratio is more preferably 0.05 or more and 0.6 or less, and further preferably 0.5 or less.

[0044] In Al / (M + Al) which is the defining formula of the aluminum coverage ratio, "M" represents the number of moles of M element. "Al" represents the number of moles of aluminum. When two or more kinds of M elements are contained in the resin composition, "M" represents the total sum of the number of moles of all M elements. The method for measuring the aluminum coverage ratio by XPS will be described in the examples below.

[0045] In relation to the aluminum coverage ratio, from the viewpoints of suppressing leakage current and improving the dispersibility of the coated particles with respect to the resin, the proportion of the aluminum element in terms of the mass of all the particles contained in the resin composition is preferably 0.2% by mass or more and 3.0% by mass or less, more preferably 0.3% by mass or more and 2.5% by mass or less, and further preferably 0.5% by mass or more and 2.0% by mass or less.

[0046] The proportion of aluminum element in terms of the mass relative to all the particles contained in the resin composition can be measured by ICP emission spectrometry.

[0047] From the viewpoints of suppressing leakage current and improving dispersibility in the resin, it is also advantageous to control the particle diameter of the coated particles having a core portion and a coating layer covering the core portion. From this viewpoint, the volume-based cumulative particle diameter D at 50% by volume of the above-mentioned coated particles contained in the resin composition based on the laser diffraction scattering particle size distribution measurement method 50 is preferably 0.01 μm or more and 3.0 μm or less, more preferably 0.05 μm or more and 1.0 μm or less, and still more preferably 0.1 μm or more and 0.5 μm or less. When only coated particles are contained in the resin composition, the particle diameter D 50 is the particle diameter D of the coated particles 50 . On the other hand, when the resin composition contains coated particles and other particles, the particle diameter D is measured for all the particles 50 . In order to manufacture particles with a particle diameter D 50 within this range, for example, in the case of coated particles, the particle diameter of the core portion as the raw material of the coated particles can be adjusted, or the thickness of the coating layer formed on the surface of the core portion can be adjusted.

[0048] Regarding the particle diameter of the particles contained in the resin composition, the particles contained in the resin composition can have various shapes. For example, spherical, polyhedral, flat, needle-like, spindle-like, amorphous, and other shapes can be cited. These shapes can also be used in combination. The shape of the coated particles mainly depends on the shape of the core portion, and the shape of the core portion is roughly reflected in the shape of the coated particles.

[0049] In order to manufacture coated particles by providing a coating layer on the surface of the core portion, various methods can be adopted. For example, a media mill device such as a bead mill or a ball mill is used to disperse the raw material particles for the core portion (hereinafter, this particle is also referred to as "core particle") in a dispersion medium such as water. When an alkaline raw material is used in the aluminum source compound, the pH of the dispersion liquid thus obtained is adjusted to be alkaline (for example, pH = 11 or more and 13 or less) by an alkaline substance. The purpose is to make it easier for the aluminum source compound added in the subsequent process to dissolve in water. If the aluminum source compound is added in a pH region lower than this pH region, although hydrated oxides of aluminum are generated, aggregated particulate hydrated oxides are generated, and it is difficult to form a film-like portion. As the alkaline substance, for example, hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide, and hydroxides of alkaline earth metals such as calcium hydroxide can be used.

[0050] Before adding an alkaline substance to the dispersion, it is preferable to raise the temperature of the dispersion. The heating temperature is preferably set to 30 °C or higher and 65 °C or lower, more preferably 50 °C or higher and 65 °C or lower, and still more preferably 50 °C or higher and 60 °C or lower. By setting the temperature conditions to this mild range, a film-like portion containing hydrated aluminum oxide can be smoothly formed in the subsequent process.

[0051] An alkaline aluminum source compound such as sodium aluminate is added to the dispersion that has become alkaline. From the aspect of being able to smoothly form a film-like portion containing hydrated aluminum oxide, it is preferable to add the aluminum source compound slowly. Next, an acidic substance is added to the dispersion to lower the pH of the dispersion to the neutral region or the weakly acidic region (for example, pH = 4.5 or higher and 7 or lower). Thereby, hydrated aluminum oxide is formed on the surface of the core particles, and the target coated particles are obtained. Then, aging is performed as needed, and further washing and drying are carried out. As the acidic substance, various inorganic acids such as sulfuric acid and hydrochloric acid can be used. This method is also called the "A method". The heating of the dispersion within the above temperature range is preferably continued until the aging is completed.

[0052] When an acidic raw material such as aluminum nitrate is used in the aluminum source compound, the pH of the dispersion is adjusted to acidic (for example, pH = 2 or higher and 4 or lower) with an acidic substance. The purpose is to make it easier for the aluminum source compound added in the subsequent process to dissolve in water. If the aluminum source compound is added in a pH region higher than this pH region, although hydrated aluminum oxide is formed, aggregated particulate hydrated oxide is formed, and it is difficult to form a film-like portion. As the acidic substance, for example, hydrochloric acid, sulfuric acid, etc. can be used.

[0053] Before adding an acidic substance to the dispersion, it is preferable to raise the temperature of the dispersion. The heating temperature is preferably set to 30 °C or higher and 65 °C or lower, more preferably 50 °C or higher and 65 °C or lower, and still more preferably 50 °C or higher and 60 °C or lower. By setting the temperature conditions to this mild range, a film-like portion containing hydrated aluminum oxide can be smoothly formed in the subsequent process.

[0054] An acidic aluminum source compound such as aluminum nitrate is added to the dispersion that has become acidic. From the aspect of being able to smoothly form a film-like portion containing hydrated aluminum oxide, it is preferable to add the aluminum source compound slowly. Next, an alkaline substance is added to the dispersion to raise the pH of the dispersion to the neutral region or the weakly acidic region. Thereby, hydrated aluminum oxide is formed on the surface of the core particles, and the target coated particles are obtained. Then, aging is performed as needed, and further washing and drying are carried out. As the alkaline substance, hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide, and hydroxides of alkaline earth metals such as calcium hydroxide can be used. This method is also called the "B method". The heating of the dispersion within the above temperature range is preferably continued until the aging is completed.

[0055] In the above Method A, the pH of the dispersion is temporarily increased to the alkaline side and then decreased to the acidic side to form a compound containing aluminum on the surface of the core particles. In Method B, the pH of the dispersion is temporarily decreased to the acidic side and then increased to the alkaline side to form a compound containing aluminum on the surface of the core particles. Instead of these methods, it is also possible to simultaneously add an aluminum source compound such as sodium aluminate and aluminum nitrate, and an acidic substance such as hydrochloric acid or a basic substance such as sodium hydroxide to the dispersion containing the core particles to form a hydrated oxide of aluminum on the surface of the core particles, thereby obtaining the target coated particles. This method is also referred to as "Method C".

[0056] In Method C, the addition amount of the acidic substance or the basic substance is preferably an amount that makes the pH of the dispersion fall within the neutral region or the weakly acidic region. Then, aging is carried out as needed, followed by further washing and drying.

[0057] In Method C, from the aspect of being able to smoothly form a film-like portion of the hydrated oxide containing aluminum, it is preferable to slowly add the aluminum source compound and the acidic substance or the basic substance. If the aluminum source compound and the acidic substance or the basic substance are added together, although a hydrated oxide of aluminum will be formed, the tendency to form aggregated particulate hydrated oxide becomes higher, making it difficult to form a film-like portion.

[0058] In Method C, it is also possible to carry out a step of adding a basic substance between aging and washing to slightly increase the pH of the dispersion. The purpose of this step is to accelerate the sedimentation of the slurry and shorten the time of the washing step. The addition of the basic substance is preferably such that the pH of the dispersion is within the range of 7 or more and 7.5 or less.

[0059] In addition, in Method C, it is also possible not to use a media mill for the dispersion step of the core particles into the dispersion medium. That is, it is also possible to simultaneously add the aluminum source compound and the acidic substance to the dispersion in a state where the core particles are added to the dispersion medium and gently mixed.

[0060] In Method C, it is also preferable to continue heating the dispersion within the temperature range used in Method A and Method B until the end of aging.

[0061] The above Method A, Method B, and Method C are wet methods, but they can also be replaced by a dry method to produce coated particles. Hereinafter, this dry method is also referred to as "Method D". In Method D, a mixer such as a shear stirring type is used to dry-mix core particles adjusted to a specified particle size with alumina sol, i.e., a colloidal solution of hydrated aluminum oxide, so that the alumina sol firmly adheres to the surface of the core particles. During dry mixing, from the viewpoint of smoothly forming the coating layer, it is preferable to add a small amount of an organic solvent such as 2-propanol. As the conditions for dry mixing, for example, the filling rate of the container is set to 70% or less for the purpose of suppressing heat generation caused by mixing, or the humidity is set to 50% RH or less for the purpose of avoiding the influence of moisture absorption.

[0062] The above description is for coated particles. Next, the resin used together with the coated particles will be described. The resin used in the present invention can be a suitable type of resin according to the specific use of the resin composition of the present invention. For example, a thermosetting resin and a thermoplastic resin can be used as the resin. When the resin composition of the present invention is used for the dielectric layer of a capacitor element, it is preferable to use a thermosetting resin. The thermosetting resin includes a C-stage resin that has completed curing, a B-stage resin in a semi-cured state before curing is completed, and an uncured resin.

[0063] When the resin contained in the resin composition of the present invention is a thermosetting resin, as such a thermosetting resin, it is preferably selected from at least one of the group consisting of an epoxy resin, a polyphenylene ether resin, an aromatic polyamide resin, a polyamideimide resin, a polyimide resin, an active ester resin, a phenolic resin, and a diamine compound. These resins can be used alone or in combination of two or more.

[0064] From the viewpoint of further improving the dispersibility of the coated particles in the resin and improving the adhesiveness between the metal foil and the resin composition described later, as the resin, it is preferable to use an epoxy resin, an aromatic polyamide resin, a polyimide resin, an active ester resin, a phenolic resin, and a diamine compound.

[0065] The resin composition contains the above-mentioned coated particles and may also contain particles other than the coated particles as required. The ratio of the resin and all the particles contained in the resin composition can be appropriately set according to the specific use of the resin composition. When the resin composition is used as, for example, a dielectric layer of a capacitor element, from the viewpoint of achieving a balance between an increase in capacitance and the strength of the dielectric layer, the ratio of all the particles contained in the resin composition is preferably 30 parts by mass or more and 90 parts by mass or less, more preferably 60 parts by mass or more and 85 parts by mass or less, and still more preferably 70 parts by mass or more, based on 100 parts by mass of the solid content of the resin composition. Regarding the ratio of all the particles contained in the resin composition, the resin component in the resin composition can be burned off, and the ratio can be measured based on the mass of the remaining particles.

[0066] In the resin composition, in addition to the above-mentioned coated particles, components that can improve various properties of the resin composition may also be contained. As such components, for example, particles belonging to the metal oxides represented by the above M x O y and not having the above-mentioned coating layer (hereinafter, such particles are also referred to as "non-coated particles") can be cited. In the resin composition, by further containing non-coated particles in addition to the coated particles, an effect of suppressing a decrease in the capacitance of the dielectric layer can be achieved.

[0067] From the viewpoint of making the above effect more significant, the ratio of the non-coated particles is preferably 5 parts by mass or more and 50 parts by mass or less, more preferably 40 parts by mass or less, and still more preferably 30 parts by mass or less, based on 100 parts by mass of the total of the coated particles and the non-coated particles.

[0068] The type of M element contained in the coated particles and the type of M element contained in the non-coated particles may be the same or different. For example, the coated particles may be particles of barium titanate covered with a coating layer of hydrated oxide containing aluminum, and the non-coated particles may be particles of barium titanate without a coating layer.

[0069] In addition, the shapes and particle diameters of the coated particles and the non-coated particles may be the same or different.

[0070] In the resin composition, in addition to the above-mentioned metal oxide particles such as the coated particles and the non-coated particles, other types of particles may also be contained. As such particles, for example, particles of barium sulfate can be cited. By further containing particles of barium sulfate in the resin composition, an effect of improving the rheology (fluidity) of the coating liquid prepared by forming a thin layer of the resin composition into a film shape and making the operation of the coating liquid easier can be achieved.

[0071] From the viewpoint of making the above effects more remarkable, it is preferable to contain 0.16 parts by mass or more and 3.2 parts by mass or less of barium sulfate particles, more preferably 0.24 parts by mass or more and 2.8 parts by mass or less, and still more preferably 0.32 parts by mass or more and 2.4 parts by mass or less, based on 100 parts by mass of the solid content of the resin composition.

[0072] From the same viewpoint, the proportion of the barium sulfate particles is preferably 0.2 parts by mass or more and 4.0 parts by mass or less, more preferably 3.5 parts by mass or less, and still more preferably 3.0 parts by mass or less, based on 100 parts by mass of the total of the coated particles, non-coated particles, and barium sulfate particles.

[0073] The average particle diameter of the barium sulfate particles observed by a scanning electron microscope is preferably 0.1 μm or more and 5 μm or less, more preferably 3 μm or less, and still more preferably 1.5 μm or less. By using barium sulfate particles having a particle diameter in this range, the rheology (fluidity) of the above coating liquid is further improved, and thus it is preferable. It should be noted that the shape of the barium sulfate particles is not particularly limited, and various shapes such as spherical and polyhedral can be adopted. Regarding the average particle diameter, for example, 5 or more, preferably 10 or more particles can be observed by a scanning electron microscope, and the average particle diameter can be calculated using image analysis software from the obtained electron microscope photographs.

[0074] When the resin composition contains coated particles and other particles (for example, the above non-coated particles, barium sulfate particles), the value of the atomic ratio Al / (M + Al) is determined by XPS measurement of all the particles contained in the resin composition.

[0075] Specifically, the resin composition is heat-treated in a high-temperature oven (for example, in an air atmosphere, the maximum temperature is 500 °C for 60 minutes) to burn off the resin component, and the obtained powder is subjected to the XPS measurement described below, whereby the above atomic ratio can be quantified. It should be noted that whether the resin component is completely burned out can be confirmed by obtaining the weight reduction data of TG-DTA.

[0076] The resin composition of the present invention can be used alone or in combination with other components according to its specific use. When the resin composition of the present invention is used as a dielectric layer of a capacitor element, for example, it is preferably used in the form of a thin film-like layer. In this case, from the viewpoint of achieving the balance between the increase in the capacitance of the dielectric layer and the strength of the dielectric layer, the thickness of the cured thin layer is preferably 15 μm or less, more preferably 8 μm or less, and still more preferably 4 μm or less. In addition, the thickness of the thin layer is preferably 0.2 μm or more, and still more preferably 0.5 μm or more.

[0077] In order to form the resin composition of the present invention into a thin film-like layer, for example, a coating liquid can be prepared by mixing covering particles, a resin, and an organic solvent capable of dissolving the resin. The coating liquid is applied onto an object (such as a metal foil described later) to form a coating film, and the coating film is dried to obtain the same. When the resin is a thermosetting resin, the coating film obtained by drying is in an uncured state, and by heating it to a specified temperature, it can be changed into a B-stage, that is, a semi-cured coating film. The B-stage coating film can be changed into a C-stage, that is, a fully cured coating film by further heating it.

[0078] As one mode of using the resin composition of the present invention in combination with other components, there can be cited a mode of forming a resin composition layer (hereinafter also referred to as "resin composition layer") on at least one surface of a metal foil to obtain a metal foil with resin. Regarding the resin composition layer in the metal foil with resin, when the resin contained in the resin composition layer is a thermosetting resin, it is preferred that the thermosetting resin is in a B-stage state before curing is completed. Thereby, the adhesion between the metal foil and the resin composition layer that is practically suitable can be ensured.

[0079] The thickness of the resin composition layer in the metal foil with resin is preferably the same as the thickness of the above-mentioned thin film-like layer.

[0080] The resin composition layer can be provided on at least one surface of the metal foil, or can be provided on each surface of the metal foil according to the use of the metal foil with resin.

[0081] As the metal foil, foils formed of various metals can be used. For example, there can be cited copper foil, aluminum foil, stainless steel foil, nickel foil, titanium foil, and foils formed by laminating multiple of any of them, etc. In particular, from the viewpoints of economy and availability, it is preferred to use copper foil. The metal foil can be any of a rolled foil, an electrolytic foil, and a vapor deposition foil.

[0082] The thickness of the metal foil is not particularly limited, and it can be determined according to the specific use of the metal foil with resin, but it is preferably 0.1 μm or more and 100 μm or less, more preferably 0.5 μm or more and 70 μm or less, further preferably 2 μm or more and 70 μm or less, particularly preferably 10 μm or more and 70 μm or less, and most preferably 10 μm or more and 35 μm or less. If the thickness is within the above range, processes such as the MSAP (modified semi-additive process) method, the SAP (semi-additive process) method, and the subtractive method, which are conventional pattern formation methods for forming wirings of printed circuit boards, can be adopted. However, when the thickness of the metal foil is, for example, 10 μm or less, etc., the metal foil with resin of the present invention can also be a metal foil having a resin layer formed on the surface of the metal foil of a metal foil with a carrier having a release layer and a carrier in order to improve workability.

[0083] From the viewpoint of sufficiently ensuring the thickness of the resin composition layer and sufficiently increasing the capacitance of the resin composition layer, it is preferable that the surface roughness of the surface of the metal foil facing the resin composition layer is low. From this viewpoint, when the ten-point height of unevenness Rzjis measured in accordance with JIS B0601-2001 is used to represent the surface roughness of the surface of the metal foil facing the resin composition layer, Rzjis is preferably 2.0 μm or less, more preferably 1.5 μm or less, still more preferably 1.0 μm or less, and particularly preferably 0.5 μm or less. Thereby, it is easy to form a thin and uniform resin composition layer. The lower limit value of the ten-point height of unevenness Rzjis of the surface of the metal foil facing the resin composition layer is not particularly limited, and from the viewpoint of improving the adhesion to the resin composition layer, Rzjis is preferably 0.005 μm or more, more preferably 0.01 μm or more, still more preferably 0.05 μm or more.

[0084] Regarding the surface of the metal foil facing the resin composition layer, the maximum peak height Sp measured in accordance with ISO25178 is preferably 0.05 μm or more and 3.3 μm or less. More preferably, it is 0.06 μm or more and 3.1 μm or less, still more preferably 3.0 μm or less, and particularly preferably 0.07 μm or more and 2.9 μm or less. By controlling the surface properties of the metal foil in this way, a metal foil with resin that can exhibit excellent characteristics in terms of withstand voltage and peel strength while ensuring a high capacitance can be obtained.

[0085] From the same viewpoint, regarding the surface of the metal foil facing the resin composition layer, the root mean square slope Sdq measured in accordance with ISO25178 is preferably 0.01 or more and 2.3 or less. More preferably, it is 0.02 or more and 2.2 or less, still more preferably 0.03 or more and 2.0 or less, and particularly preferably 0.04 or more and 1.8 or less.

[0086] Furthermore, from the same viewpoint, regarding the surface of the metal foil facing the resin composition layer, the kurtosis Sku measured in accordance with ISO25178 is preferably 2.6 or more and 4.0 or less, more preferably 2.7 or more and 3.8 or less, still more preferably 2.7 or more and 3.7 or less.

[0087] As another mode of using the resin composition of the present invention in combination with other components, a metal-clad laminate including a first metal foil, a second metal foil, and a resin composition layer sandwiched between the two metal foils can also be cited. Regarding the resin composition layer in the metal-clad laminate, when the resin contained in the resin composition layer is a thermosetting resin, the thermosetting resin is preferably a cured product. Thereby, practically suitable adhesion to the first metal foil and the second metal foil can be ensured. In addition, when manufacturing the metal-clad laminate, the adhesion of the bonding interface between the resin composition layers or the bonding interface between the resin composition layer and the metal foil is improved, so that an excellent formability effect is achieved.

[0088] The types of the first metal foil and the second metal foil in the metal-clad laminate may be the same or different. The type of the metal foil may be the same as the above-mentioned metal foil with resin.

[0089] In addition, the thicknesses of the first metal foil and the second metal foil in the metal-clad laminate may be the same or different. The thickness of the metal foil may be the same as the above-mentioned metal foil with resin.

[0090] From the viewpoint of sufficiently ensuring the thickness of the resin composition layer and sufficiently increasing the capacitance of the resin composition layer, it is preferable that the surface roughness of the surfaces of the first metal foil and the second metal foil facing the resin composition layer is low. From this viewpoint, when the surface roughness of the surfaces of the first metal foil and the second metal foil facing the resin composition layer is represented by the ten-point height of unevenness Rzjis measured according to JIS B0601-2001, Rzjis is preferably 2.0 μm or less, more preferably 1.5 μm or less, further preferably 1.0 μm or less, and particularly preferably 0.5 μm or less. Thereby, it is easy to form a thin and uniform resin composition layer.

[0091] The maximum peak height Sp of at least one of the first metal foil and the second metal foil measured according to ISO 25178 on the surface facing the resin composition layer is preferably 0.05 μm or more and 3.3 μm or less. More preferably, it is 0.06 μm or more and 3.1 μm or less, further preferably 3.0 μm or less, and particularly preferably 0.07 μm or more and 2.9 μm or less. By controlling the surface properties of the metal foil in this way, a metal-clad laminate can be obtained that exhibits excellent characteristics in terms of withstand voltage and peel strength while ensuring a high capacitance.

[0092] Further, from the same perspective, the root mean square slope Sdq measured in accordance with ISO25178 of the opposite surface of at least one of the first metal foil and the second metal foil to the resin composition layer is preferably 0.01 or more and 2.3 or less. More preferably, it is 0.02 or more and 2.2 or less, still more preferably 0.03 or more and 2.0 or less, and particularly preferably 0.04 or more and 1.8 or less.

[0093] Furthermore, from the same perspective, the kurtosis Sku measured in accordance with ISO25178 of the opposite surface of at least one of the first metal foil and the second metal foil to the resin composition layer is preferably 2.6 or more and 4.0 or less, more preferably 2.7 or more and 3.8 or less, and still more preferably 2.7 or more and 3.7 or less.

[0094] The metal-clad laminate has a structure in which a resin composition layer as a dielectric layer is disposed between the first metal foil and the second metal foil. Therefore, the metal-clad laminate can be used as a capacitor element. Since the resin in the metal-clad laminate contains the above-described covering particles, by using the metal-clad laminate as a capacitor element, the leakage current of the capacitor element can be suppressed, and in addition, the withstand voltage can be increased, and the capacitance can be further increased.

[0095] Specifically, the leakage current when a DC voltage of 50 V is applied between the first metal foil and the second metal foil in the metal-clad laminate is preferably 150 μA / cm 2 Hereinafter, more preferably 100 μA / cm 2 Hereinafter, still more preferably 50 μA / cm 2 or less, a low value.

[0096] In addition, the withstand voltage per unit thickness of the resin composition layer when a DC voltage is applied between the first metal foil and the second metal foil in the metal-clad laminate is preferably 50 V / μm or more, more preferably 75 V / μm or more, and still more preferably 100 V / μm or more, a high value. The unit thickness mentioned here means that the thickness of the resin composition layer is 1 μm.

[0097] Furthermore, the capacitance per unit area of the metal-clad laminate at a frequency of 1 kHz is preferably 10 nF / in 2 or more, more preferably 20 nF / in 2 or more, still more preferably 30 nF / in 2 or more, a high value. The unit area mentioned here means in 2 (1 square inch).

[0098] Furthermore, the peel strength between the first metal foil and / or the second metal foil of the metal-clad laminate and the resin composition layer is preferably a high value of 0.3 kN / m or more, more preferably 0.4 kN / m or more, and still more preferably 0.5 kN / m or more.

[0099] The metal-clad laminate is preferably manufactured as follows: Prepare a set of the resin-coated metal foils described above, overlap the two with the resin composition layers (the resin composition layers are preferably in the B-stage.) in the resin-coated metal foils facing each other, and completely cure the resin composition layers by applying pressure under heating.

[0100] The above resin-coated metal foil and metal-clad laminate having the layer of the resin composition of the present invention are suitable as materials for printed circuit boards having a dielectric layer.

[0101] The present invention has been described based on preferred embodiments, but the present invention is not limited to the above embodiments. For example, in the first metal foil and the second metal foil of the above metal-clad laminate, a carrier foil may be disposed on the surface on the side not facing the resin composition layer with a release layer interposed therebetween.

[0102] In addition, in the metal foil of the above resin-coated metal foil, a carrier foil may be disposed on the surface on the side not facing the resin composition layer with a release layer interposed therebetween.

[0103] Examples

[0104] Hereinafter, the present invention will be described in more detail by way of examples. However, the scope of the present invention is not limited to these examples. Unless otherwise specified, "%" and "parts" represent "mass%" and "mass parts", respectively.

[0105] 〔Production Example 1〕

[0106] 80 kg of spherical barium titanate particles having a particle size D 50 of 0.1 μm and having a perovskite crystal structure were mixed with 700 kg of water, and the barium titanate particles were dispersed in water using a bead mill to obtain a dispersion.

[0107] The dispersion was heated to 60°C. An aqueous sodium hydroxide solution was added to the dispersion to adjust the pH of the dispersion to about 12. Then, an aqueous solution in which 3050 g of sodium aluminate was dissolved was slowly added to the dispersion.

[0108] Next, an aqueous sulfuric acid solution was added to the dispersion to lower the pH of the dispersion to about 5, and a covering layer of hydrated aluminum oxide was formed on the surface of the barium titanate particles.

[0109] After 30 minutes of aging, the particles are washed with water until the conductivity of the aqueous phase reaches 100 μS / cm or less. Then, the particles are dried at 150 °C to obtain the target coated particles. In addition, as a by-product, barium sulfate having an average particle size of 0.8 μm as observed by a scanning electron microscope is obtained. For the obtained coated particles, the formation of hydrated aluminum oxide is confirmed by a combination of H-NMR, Al-NMR, AES, and XPS evaluations (the same applies to the following Production Examples).

[0110] 〔Production Example 2〕

[0111] 700 g of spherical barium titanate particles having a particle size D 50 of 0.1 μm and having a perovskite crystal structure are mixed with 7000 g of water, and the barium titanate particles are dispersed in water using a bead mill to obtain a dispersion.

[0112] The dispersion is heated to 60 °C. An aqueous hydrochloric acid solution and an aqueous sodium aluminate solution are simultaneously and slowly added to the dispersion to adjust the pH of the dispersion to about 5, thereby forming a coating layer of hydrated aluminum oxide on the surface of the barium titanate particles. The amount of sodium aluminate added is 27 g.

[0113] After 30 minutes of aging, the particles are washed with water until the conductivity of the aqueous phase reaches 100 μS / cm or less. Then, the particles are dried at 150 °C to obtain the target coated particles.

[0114] 〔Production Example 3〕

[0115] 700 g of spherical barium titanate particles having a particle size D 50 of 0.1 μm are mixed with 7000 g of water, and the barium titanate particles are dispersed in water using a bead mill to obtain a dispersion.

[0116] The dispersion is heated to 60 °C. An aqueous hydrochloric acid solution and an aqueous sodium aluminate solution are simultaneously and slowly added to the dispersion to adjust the pH of the dispersion to about 5, thereby forming a coating layer of hydrated aluminum oxide on the surface of the barium titanate particles. The amount of sodium aluminate added is 27 g.

[0117] After 30 minutes of aging, an aqueous sodium hydroxide solution is added to the dispersion to raise the pH of the dispersion to about 7. Then, the particles are washed with water until the conductivity of the aqueous phase reaches 100 μS / cm or less. Then, the particles are dried at 150 °C to obtain the target coated particles.

[0118] 〔Production Example 4〕

[0119] 700 g of spherical barium titanate particles having a particle size D 50700 g of spherical barium titanate particles with a particle size D of 0.1 μm were mixed with 7000 g of water to obtain a dispersion. Except for not performing dispersion using a bead mill, the same procedure as in Production Example 2 was carried out to obtain the target coated particles.

[0120] [Production Example 5]

[0121] The spherical barium titanate particles with a particle size D 50 of 0.1 μm and 700 g were mixed with 7000 g of water, and the barium titanate particles were wet-crushed and dispersed in water using a bead mill to obtain a dispersion.

[0122] Except for setting the addition amount of sodium aluminate to 19 g, the same procedure as in Production Example 2 was carried out to obtain the target coated particles.

[0123] [Production Example 6]

[0124] The spherical barium titanate particles with a particle size D 50 of 0.1 μm and 700 g were mixed with 7000 g of water, and the barium titanate particles were dispersed in water using a bead mill to obtain a dispersion.

[0125] Except for setting the addition amount of sodium aluminate to 68 g, the same procedure as in Production Example 2 was carried out to obtain the target coated particles.

[0126] [Production Example 7]

[0127] The spherical barium titanate particles with a particle size D 50 of 0.1 μm and 700 g were mixed with 7000 g of water, and the barium titanate particles were dispersed in water using a bead mill to obtain a dispersion.

[0128] The dispersion was heated to 60 °C. An aqueous sodium hydroxide solution was added to the dispersion to adjust the pH of the dispersion to approximately 12. Then, an aqueous sodium aluminate solution was slowly added to the dispersion. The addition amount of sodium aluminate was 27 g.

[0129] Next, an aqueous hydrochloric acid solution was added to the dispersion to lower the pH of the dispersion to approximately 5, and a hydrated aluminum oxide coating layer was formed on the surface of the barium titanate particles.

[0130] After aging for 30 minutes, the particles were washed with water until the conductivity of the aqueous phase reached 100 μS / cm or less, and then the particles were dried at 150 °C to obtain the target coated particles.

[0131] [Production Example 8]

[0132] The spherical barium titanate particles with a particle size D 50 of 0.1 μm and 200 g were mixed with 2000 g of water, and the barium titanate particles were dispersed in water using a bead mill to obtain a dispersion.

[0133] Heat the dispersion to 60 °C. While slowly adding an aqueous sodium hydroxide solution and an aqueous aluminum nitrate solution to the dispersion simultaneously, adjust the pH of the dispersion to approximately 5 to form a covering layer of hydrated aluminum oxide on the surface of the barium titanate particles. The addition amount of aluminum nitrate is 30 g.

[0134] After aging for 30 minutes, wash the particles with water until the conductivity of the aqueous phase reaches 100 μS / cm or less. Then, dry the particles at 150 °C to obtain the target covered particles.

[0135] 〔Production Example 9〕

[0136] In this production example, covered particles are produced by a dry method.

[0137] Crush 100 g of barium titanate particles using a mixer (Force Mill manufactured by OSAKA CHEMICAL Co., Ltd.) to form spherical particles with a particle size D 50 of 0.15 μm.

[0138] Mix the crushed barium titanate particles, alumina sol (alumina sol - 10A manufactured by Kawaken Fine Chemicals Co., Ltd.) and 2 - propanol using a mixer (Force Mill manufactured by Osaka Chemical Co., Ltd.) under the conditions of a filling rate of 40% and a humidity of 40% RH to form a covering layer of hydrated aluminum oxide on the surface of the barium titanate particles. The amount of alumina sol used is 20 g. The amount of 2 - propanol used is 2 g.

[0139] Then, dry the particles at 110 °C to obtain the target covered particles.

[0140] 〔Production Example 10〕

[0141] This production example corresponds to the example of Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2020 - 57667).

[0142] Mix 700 g of spherical barium titanate particles having a perovskite - type crystal structure with 7000 g of water, and use a bead mill to disperse the barium titanate particles in water to obtain a dispersion.

[0143] Heat the dispersion to 70 °C. The pH of the dispersion at this time is approximately 9. Add an aqueous sodium aluminate solution to the dispersion. The addition amount is 106 g. At this time, precipitation of a water - insoluble compound containing aluminum is observed. The pH of the dispersion at this time is approximately 10. Then, add an aqueous sodium hydroxide solution to the dispersion to adjust the pH of the dispersion to approximately 11.

[0144] Next, an aqueous hydrochloric acid solution was added to the dispersion to lower the pH of the dispersion to about 7, and a covering layer of hydrated oxide of aluminum was formed on the surface of the barium titanate particles.

[0145] After aging for 30 minutes, the particles were washed with water until the conductivity of the aqueous phase reached 100 μS / cm or less, and then the particles were dried at 150 °C to obtain the target covered particles.

[0146] 〔Production Example 11〕

[0147] This production example is an example in which the amount of the covering layer attached is significantly increased compared to Production Example 1.

[0148] 700 g of spherical barium titanate particles having a perovskite-type crystal structure were mixed with 7000 g of water, and the barium titanate particles were dispersed in water using a bead mill to obtain a dispersion.

[0149] The dispersion was heated to 60 °C. An aqueous sodium hydroxide solution was added to the dispersion to adjust the pH of the dispersion to about 12. Next, an aqueous sodium aluminate solution was added to the dispersion. The addition amount of sodium aluminate was 106 g.

[0150] Next, an aqueous hydrochloric acid solution was added to the dispersion to lower the pH of the dispersion to about 7, and a covering layer of hydrated oxide of aluminum was formed on the surface of the barium titanate particles.

[0151] After aging for 30 minutes, the particles were washed with water until the conductivity of the aqueous phase reached 100 μS / cm or less, and then the particles were dried at 150 °C to obtain the target covered particles.

[0152] 〔Production Example 12〕

[0153] Except for using spherical barium titanate particles having a particle size D 50 of 0.2 μm, the same procedure as in Production Example 7 was carried out to obtain the target covered particles.

[0154] 〔Production Example 13〕

[0155] Except that the addition amount of sodium aluminate was set to 20 g, the same procedure as in Production Example 12 was carried out to obtain the target covered particles.

[0156] 〔Production Example 14〕

[0157] Except that the addition amount of sodium aluminate was set to 13 g, the same procedure as in Production Example 12 was carried out to obtain the target covered particles.

[0158] 〔Production Example 15〕

[0159] Except that the addition amount of sodium aluminate was set to 7 g, the same procedure as in Production Example 12 was carried out to obtain the target covered particles.

[0160] 〔Examples 1 to 13 and Comparative Examples 1 and 2〕

[0161] The covering particles obtained in Production Examples 1 to 15 (barium sulfate was also included in Production Example 1) and the dispersant components were mixed into a cyclopentanone solvent, and slurried using a disperser.

[0162] After confirming the slurrying, a varnish of the resin components of Formulation Example 1 shown in Table 1 below was kneaded to prepare a coating solution. The mass ratios of the covering particles, other particles, and the resin components in the coating solution are shown in Table 2.

[0163] Using a bar coater, the obtained coating solution was coated on a copper foil (manufactured by Mitsui Mining & Smelting Co., Ltd., thickness 18 μm, surface roughness Rzjis = 0.5 μm) such that the thickness of the dried resin composition layer became about 1.5 μm, and then dried in an oven heated to 160°C for 3 minutes to make the resin composition in a semi-cured state. Thus, a copper foil with a resin was obtained.

[0164] Two pieces of copper foils with resins were laminated such that the resin surfaces in the copper foils faced each other, and vacuum pressing was performed at a pressure of 40 kgf / cm 2 and 200°C for 90 minutes to make the resin composition in a cured state. A copper-clad laminate including such a cured resin composition as a dielectric layer was obtained. The results of measuring the thickness of the resin composition layer in the obtained copper-clad laminate are shown in Table 2.

[0165] 〔Example 14〕

[0166] The covering particles obtained in Production Example 1, spherical barium titanate particles having a perovskite-type crystal structure and not having a covering layer (D 50 : 0.3 μm) and the dispersant components were mixed into a cyclopentanone solvent, and slurried using a disperser.

[0167] After confirming the slurrying, a varnish of the resin components of Formulation Example 1 shown in Table 1 was kneaded to prepare a coating solution. The mass ratios of the covering particles, other particles, and the resin components in the coating solution are shown in Table 2.

[0168] Except for this, a copper-clad laminate was obtained in the same manner as in Example 1. The thickness of the resin composition layer in the obtained copper-clad laminate is shown in Table 2.

[0169] 〔Example 15〕

[0170] The covering particles obtained in Production Example 1, spherical barium titanate particles having a perovskite-type crystal structure and not having a covering layer (D 50 : 0.2 μm) and the dispersant components were mixed into a cyclopentanone solvent, and slurried using a disperser.

[0171] After confirming the slurring, a varnish of the resin composition of Formulation Example 1 shown in Table 1 was kneaded to prepare a coating solution. The mass ratios of the covering particles, other particles, and resin component in the coating solution are shown in Table 2.

[0172] In addition, a double-sided copper-clad laminate was obtained in the same manner as in Example 1. The thickness of the resin composition layer in the obtained copper-clad laminate is shown in Table 2.

[0173] 〔Comparative Example 3〕

[0174] Barium titanate particles (D 50 : 0.1 μm) and a dispersant component were mixed into a cyclopentanone solvent, and slurried using a disperser.

[0175] After confirming the slurring, a varnish of the resin composition of Formulation Example 1 shown in Table 1 was kneaded to prepare a coating solution. The mass ratios of the barium titanate particles and resin component in the coating solution are shown in Table 2.

[0176] In addition, a double-sided copper-clad laminate was obtained in the same manner as in Example 1. The thickness of the resin composition layer in the obtained copper-clad laminate is shown in Table 2.

[0177] 〔Examples 16 to 21〕

[0178] The covering particles obtained in Production Example 1 and a dispersant component were mixed into a cyclopentanone solvent, and slurried using a disperser.

[0179] After confirming the slurring, varnishes of the resin compositions of Formulation Examples 1 to 6 shown in Table 1 were kneaded to prepare coating solutions. The mass ratios of the covering particles and resin component in the coating solutions are shown in Table 3.

[0180] In addition, a double-sided copper-clad laminate was obtained in the same manner as in Example 1. The thickness of the resin composition layer in the obtained copper-clad laminate is shown in Table 3.

[0181] 〔Evaluation 1〕

[0182] For the copper-clad laminates obtained in the examples and comparative examples (i.e., the copper-clad laminates prepared using the particles obtained in Production Examples 1 to 15, and the copper-clad laminates obtained in Examples 14 and 15), the particle size D of the particles contained in the resin composition layer was determined using a laser diffraction / scattering particle size distribution measuring device. 50 . The results are shown in Table 4 below. When measuring, the slurries used in the respective examples and comparative examples were used.

[0183] 〔Evaluation 2〕

[0184] For the copper-clad laminates obtained in the examples and comparative examples, after stripping the copper foil, the mass ratio of aluminum element in the particles contained in the resin composition layer was measured by ICP emission spectrometry. In addition, for the resin composition layer, XPS measurement was performed using PHIQuantes manufactured by ULVAC·PHI Corporation, and the atomic ratio Al / (M + Al) was measured. These results are shown in Table 4. The details of the XPS measurement and analysis are described below.

[0185] 〔Conditions〕

[0186] ·Excitation X-ray: Monochromatic Al-Kα ray (1486.7 eV)

[0187] ·Output power: 50 W

[0188] ·Acceleration voltage: 15 kV

[0189] ·X-ray irradiation diameter:

[0190] ·X-ray scanning area: 1000 μm × 300 μm

[0191] ·Detection angle: 45°

[0192] ·Pass energy: 26.0 eV

[0193] ·Energy step: 0.1 eV / step

[0194] ·Elements to be measured: C: 1s, O: 1s, Al: 2p, Ti: 2p, Ba: 3d 5 / 2

[0195] 〔Analysis〕

[0196] The XPS data was analyzed using data analysis software ("Multi pack Ver9.9" manufactured by ULVAC·PHI Corporation). The Shirley background mode was used.

[0197] 〔Evaluation 3〕

[0198] For the copper-clad laminates obtained in the examples and comparative examples, the formability was evaluated by the following method.

[0199] In addition, for the copper-clad laminates obtained in the examples and comparative examples, the thickness, withstand voltage, leakage current, capacitance, and peel strength (circuit adhesion) between the copper foil and the resin composition layer were measured by the following methods. These results are shown in Tables 2 and 3.

[0200] 〔Evaluation of the formability of the copper-clad laminate〕

[0201] After cutting the copper-clad laminate into a size of about 8 mm in width and 5 mm in length, it was cut along the thickness direction using a fully automatic universal rotary microtome (Leica Biosystems, RM2265) to expose the cross-section. This cross-section was observed with an optical microscope (Leica Microsystems, Leica DM LM), and for the bonding interface of the resin composition layer, the presence or absence of poor adhesion was confirmed. The judgment of good or bad was evaluated according to the following criteria. The results are shown in Tables 2 and 3.

[0202] · Good: There is no poor adhesion at the bonding interface of the resin composition layer. (There is no problem with formability)

[0203] · Bad: There is poor adhesion at the bonding interface of the resin composition layer. (Poor formability)

[0204] 〔Thickness of the resin composition layer〕

[0205] For the cross-section exposed by the same procedure as the evaluation of the formability of the copper-clad laminate, it was observed with an optical microscope (Leica Microsystems, Leica DM LM), and the thickness of the resin composition layer was measured at any 5 points, and their average value was calculated. The results are shown in Tables 2 and 3.

[0206] 〔Dielectric breakdown voltage〕

[0207] A circular circuit with a diameter of 0.5 inches (12.6 mm) was fabricated by etching one side of the copper-clad laminate to obtain a measurement sample. Using this measurement sample as the object, the dielectric breakdown voltage under the condition of a voltage rise rate of 167 V / s was measured with an insulation resistance meter (manufactured by Hioki Electric Co., Ltd., Super Insulation Meter SM7110). This measurement was carried out in accordance with IPC-TM-650 2.5.6.2a.

[0208] The dielectric breakdown voltage measured above was divided by the thickness of the resin composition layer of the measurement object to calculate the dielectric breakdown voltage per unit thickness. The results are shown in Tables 2 and 3.

[0209] 〔Leakage current〕

[0210] A circular circuit with a diameter of 0.5 inches (12.6 mm) was fabricated by etching one side of the copper-clad laminate to obtain a measurement sample. Using this measurement sample as the object, the leakage current value under an applied voltage of 50 V was measured with an insulation resistance meter (manufactured by Hioki Electric Co., Ltd., Super Insulation Meter SM7110). This measurement was carried out in accordance with IPC-TM-650 2.5.6.2a. The results are shown in Tables 2 and 3.

[0211] 〔Capacitance〕

[0212] An etching process was performed on one side of a double-sided copper-clad laminate to fabricate a circular circuit with a diameter of 0.5 inches (12.6 mm), obtaining a measurement sample. Using this measurement sample, the capacitance at a frequency of 1 kHz was measured using an LCR meter (manufactured by Hioki Electric Co., Ltd., LCR HiTESTER3532-50). This measurement was carried out in accordance with IPC-TM-650 2.5.2.

[0213] The capacitance measured above was divided by the thickness of the resin composition layer being measured to calculate the capacitance equivalent to a thickness of 3 μm. The results are shown in Tables 2 and 3.

[0214] 〔Peeling Strength (Circuit Adhesion) between Copper Foil and Resin Composition Layer〕

[0215] An etching process was performed on one side of a copper-clad laminate to fabricate a linear circuit with a width of 3 mm, obtaining a measurement sample. Using this measurement sample, the circuit was peeled at a peeling speed of 50 mm / minute using a universal testing machine (Autograph) to measure the peeling strength. This measurement was carried out in accordance with IPC-TM-650 2.4.8. If the measured value is 0.3 kN / m or more, it is judged that it can be used without practical problems. The results are shown in Tables 2 and 3.

[0216] 〔Evaluation 4〕

[0217] For the coated particles obtained in Production Example 1 and Production Example 10, transmission electron microscope observation and elemental mapping were performed. The results are shown in Figure 1 and Figure 2 .

[0218] 〔Evaluation 5〕

[0219] For the coated particles obtained in Production Example 6 and Production Example 1, analysis using XAFS (X-ray Absorption Fine Structure Analysis) was performed. The results are shown in Figure 3 . In this figure, 1 represents the spectrum of Production Example 6, and 2 represents the spectrum of Production Example 1.

[0220] The detailed conditions are as described below.

[0221] 〔Conditions〕

[0222] · Measurement facility: Aichi Synchrotron Radiation Center

[0223] · Beamline: BL1N2

[0224] · Specimen holding method: Coated on an indium film

[0225] · Measurement energy: 1500 - 2000 eV

[0226] · Measurement time: 51 minutes

[0227] · Detection method: partial fluorescence yield method

[0228] · Configuration of detector and specimen: X-rays are incident at 22.5° from the perpendicular direction of the specimen surface, and X-rays are detected at 90°

[0229] · Background removal range: 1500 - 2000 eV

[0230] [Table 1]

[0231] Resin component

[0232] Component ① Component ② Component ③ Mixing Example 1 Epoxy Diamine compound Polyimide Mixing Example 2 Epoxy Active ester Polyimide Mixing Example 3 Epoxy Phenolic Polyimide Mixing Example 4 Epoxy Diamine compound Aromatic polyamide Mixing Example 5 Epoxy Active ester Aromatic polyamide Mixing Example 6 Epoxy Phenolic Aromatic polyamide

[0233] [Table 2]

[0234]

[0235] [Table 3]

[0236]

[0237] [Table 4]

[0238] <![CDATA[Particle size D 50 (μm)]]> Atomic ratio Al / (M + Al) Al content (%) Production Example 1 0.13 0.32 1.04 Production Example 2 0.15 0.36 1.00 Production Example 3 0.16 0.35 1.01 Production Example 4 0.19 0.28 0.80 Production Example 5 0.13 0.23 0.66 Production Example 6 0.21 0.62 2.28 Production Example 7 0.16 0.36 1.00 Production Example 8 0.20 0.37 1.01 Production Example 9 0.15 0.11 0.98 Production Example 10 0.29 0.47 3.82 Production Example 11 0.36 0.80 3.79 Production Example 12 0.29 0.48 1.04 Production Example 13 0.31 0.41 0.85 Production Example 14 0.30 0.30 0.51 Production Example 15 0.28 0.16 0.25 Example 10 0.18 0j0 0.91 Example 11 0.16 0.26 0.92

[0239] As can be seen from the results shown in Tables 2 and 3, the copper-clad laminates obtained in each example not only have high withstand voltage, small leakage current, and high capacitance, but also have excellent adhesion between the copper foil and the resin composition layer.

[0240] In addition, from Figure 1 the results shown, it was confirmed that in the covering particles obtained in Production Example 1, a film-like portion was formed on the surface of the core portion composed of barium titanate. In addition, based on the results of H-NMR, Al-NMR, AES, XPS, and synchrotron radiation XRD, etc., it was confirmed that the aforementioned film-like portion contains hydrated aluminum oxide.

[0241] On the other hand, from Figure 2 the results shown, it was confirmed that in the covering particles obtained in Production Example 10, aggregated particles were attached to the surface of the core portion composed of barium titanate. It is considered that the reason is that the pH of the dispersion liquid was not high enough when sodium aluminate was added to the dispersion liquid, and the heating temperature of the dispersion liquid was high. In addition, using the same method as the analysis of the above-mentioned film-like portion, it was confirmed that the above-mentioned aggregated particles contain hydrated aluminum oxide.

[0242] It should be noted that although not shown in the drawings, for the covering particles obtained in Production Examples 2 to 9 and Production Examples 12 to 15, the present inventors also confirmed that a film-like portion containing hydrated aluminum oxide was formed on the surface of the core portion composed of barium titanate.

[0243] In addition, from Figure 3As can be seen from the results shown, in the XAFS spectra of the coated particles obtained in Production Example 6 and Production Example 1, two peaks (i.e., Peak A and Peak B) were observed between 1567 eV and 1577 eV. When comparing this with relevant references of aluminum compounds such as J. Synchrotron Rad. (1999) 6.621 - 623, since it is similar to the spectrum of the 6 - coordinate structure, it is speculated that the aluminum compound in the film - like part has a 6 - coordinate structure.

[0244] Industrial Applicability

[0245] According to the present invention, there is provided a resin composition suitable for use as a dielectric layer of a capacitor element. The leakage current of the capacitor element having the resin composition as the dielectric layer is suppressed. In addition, since the resin composition has high adhesiveness, it binds well to electrodes such as metal foils.

Claims

1. A resin composition containing coated particles and a resin, wherein the coated particles have a core portion containing a metal oxide and a coating layer containing a hydrated oxide of aluminum disposed on the surface of the core portion, The metal oxide is represented by M x O y where M represents at least one element selected from the group consisting of Ba, Ti, Sr, Pb, Zr, La, Ta, Ca, and Bi, and x and y represent numbers determined by stoichiometry according to the valence of the metal element M when performing XPS analysis on the particles contained in the resin composition, the atomic ratio Al / (M + Al) is 0.05 or more and 0.7 or less, the proportion of aluminum element in terms of mass to the total mass of all the particles contained in the resin composition is 0.2% by mass or more and 3.0% by mass or less.

2. The resin composition according to claim 1, wherein, The volume median diameter D of the cumulative volume 50% of the laser diffraction scattering-based particle size distribution measurement method for the coated particles 50 is 0.01 μm or more and 3.0 μm or less.

3. The resin composition according to claim 1 or 2, wherein, the M element contains at least Ti and at least one of Ba and Sr.

4. The resin composition according to claim 1 or 2, wherein, the metal oxide is formed of a compound having a perovskite-type crystal structure.

5. The resin composition according to claim 1 or 2, further comprising particles of the metal oxide without the coating layer.

6. The resin composition according to claim 1 or 2, wherein, relative to 100 parts by mass of the solid content of the resin composition, 30 parts by mass or more and 90 parts by mass or less of the coated particles are included.

7. The resin composition according to claim 1 or 2, wherein, the resin contains at least one selected from the group consisting of an epoxy resin, a polyphenylene ether resin, an aromatic polyamide resin, a polyamideimide resin, a polyimide resin, an active ester resin, a phenolic resin, and a diamine compound.

8. The resin composition according to claim 1 or 2, further comprising particles of barium sulfate.

9. The resin composition according to claim 1 or 2, having a film-like form and a thickness of 15 μm or less.

10. A resin-coated metal foil comprising a metal foil and a layer formed of the resin composition according to any one of claims 1 to 9 provided on at least one surface of the metal foil.

11. The resin-coated metal foil according to claim 10, wherein, the metal foil is a copper foil.

12. A metal-clad laminate comprising a first metal foil, a second metal foil, and a resin composition layer sandwiched between the two metal foils, wherein the resin composition layer is formed of a cured product of the resin composition according to any one of claims 1 to 9.

13. The metal-clad laminate according to claim 12, wherein, when applying a DC voltage between the two metal foils, the withstand voltage per unit thickness of the resin composition layer is 50 V / μm or more.

14. The metal-clad laminate according to claim 12 or 13, wherein, The leakage current is 150 μA / cm when a DC voltage of 50 V is applied between the two metal foils. 2 as follows.

15. The metal-clad laminate according to claim 12 or 13, wherein, the peel strength between the metal foil and the resin composition layer is 0.3 kN / m or more.

16. A capacitor element having the metal-clad laminate according to any one of claims 12 to 15.

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